US8148294B2 - Metal-polymer composites comprising nanostructures and applications thereof - Google Patents

Metal-polymer composites comprising nanostructures and applications thereof Download PDF

Info

Publication number
US8148294B2
US8148294B2 US13/196,735 US201113196735A US8148294B2 US 8148294 B2 US8148294 B2 US 8148294B2 US 201113196735 A US201113196735 A US 201113196735A US 8148294 B2 US8148294 B2 US 8148294B2
Authority
US
United States
Prior art keywords
acid
metal
pani
dopant
substrate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US13/196,735
Other versions
US20110293820A1 (en
Inventor
Hsing-Lin Wang
Sea Ho Jeon
Nathan H. Mack
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Triad National Security LLC
Original Assignee
Los Alamos National Security LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US11/653,004 external-priority patent/US7786037B2/en
Application filed by Los Alamos National Security LLC filed Critical Los Alamos National Security LLC
Priority to US13/196,735 priority Critical patent/US8148294B2/en
Publication of US20110293820A1 publication Critical patent/US20110293820A1/en
Application granted granted Critical
Publication of US8148294B2 publication Critical patent/US8148294B2/en
Assigned to TRIAD NATIONAL SECURITY, LLC reassignment TRIAD NATIONAL SECURITY, LLC ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LOS ALAMOS NATIONAL SECURITY, LLC
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/42—Platinum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/44—Palladium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/50—Silver
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/52—Gold
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/391—Physical properties of the active metal ingredient
    • B01J35/393—Metal or metal oxide crystallite size
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/58—Fabrics or filaments
    • B01J35/59—Membranes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/65—Raman scattering
    • G01N21/658—Raman scattering enhancement Raman, e.g. surface plasmons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0203—Impregnation the impregnation liquid containing organic compounds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S977/00—Nanotechnology
    • Y10S977/70—Nanostructure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S977/00—Nanotechnology
    • Y10S977/70—Nanostructure
    • Y10S977/81—Of specified metal or metal alloy composition

Definitions

  • the present invention relates to metal-polyaniline composites, e.g., nanostructured metal-polyaniline composites, and to methods of preparation thereof.
  • PANI Polyaniline
  • PANI possesses secondary and tertiary amines in the backbone structure that can reversibly bind metal ions.
  • metal ions have a reduction potential higher than that of the PANI, the bound metal ions can be reduced to form zero-valent metals.
  • PANI can be used for the electrodeless deposition of metals from a metal ion solution.
  • the present invention describes thermally treated, dense PANI films having a variety of nanostructures on the surface, and methods for controllably depositing the nanostructures.
  • a method of forming a metal-polymer composite comprising providing a thermally-cured dense polyaniline substrate; contacting the thermally-cured dense polyaniline substrate with an acid dopant to form a doped substrate; providing a solution comprising a metal ion; and contacting the solution comprising a metal ion with the doped substrate, whereupon metal nanostructure deposits are formed on the doped substrate, wherein the deposits have a morphology which is dependent upon the acid dopant.
  • a method of forming a metal-polymer composite comprising providing a thermally-cured dense polyaniline substrate; providing a solution comprising a metal ion and an acid dopant; and contacting the solution comprising the metal ion and acid dopant with the thermally-cured dense polyaniline substrate, whereupon metal nanostructure deposits are formed on the doped substrate, wherein the deposits have a morphology which is dependent upon the acid dopant.
  • a method of performing surface-enhanced Raman spectral analysis of an analyte comprising providing a thermally-cured dense polyaniline substrate, wherein a surface of the substrate comprises metal nanostructure deposits and an acid dopant; bringing an analyte into effective contact with said metal-PANI composite; illuminating the metal-PANI composite with radiation of at least one wavelength for causing elemental-state particles to produce a plasmon field and for causing said plasmon field to interact with molecules of said analyte, in such a manner, so as to produce Raman photons; and, collecting scatted radiation emitted, from said metal-PANI composite for spectral analysis.
  • a metal-polymer composite comprising a thermally-cured dense polyaniline substrate; an acid dopant; and, metal nanostructure deposits wherein the deposits have a morphology dependent upon the acid dopant.
  • the x-axis represents wavelength in cm ⁇ 1 and the y-axis represents signal intensity
  • FIGS. 1( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 1 mM silver nitrate and doped with citric acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 2( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 10 mM silver nitrate, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 3( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with citric acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 4( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 100 mM silver nitrate and doped with citric acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 5( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with tartaric acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 6( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with phosphoric acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 7( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with camphosulfonic acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 8 ( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with mandelic acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 9 ( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with p-toluene sulfonic acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 10 ( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with polystyrene sulfonic acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • FIGS. 11( a )-( b ) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a gold nanostructure of the present invention made with 200 mM AuCl 3 with HCl, and doped with citric acid, and the corresponding SEM image of the nanostructure (b).
  • MAA mercaptobenzoic acid
  • the present invention is concerned with the metal-polyaniline composites comprising a dense-film PANI substrate, and to methods of producing these metal-polyaniline composites, wherein the metal forms various nanostructures on the surface of the composite.
  • the present invention is also concerned with the use of such metal-polyaniline composites, e.g., such nanostructured metal-polyaniline composites, in applications employing Surface Enhanced Raman Scattering (SERS).
  • SERS Surface Enhanced Raman Scattering
  • Thermally-cured dense polyaniline substrate means a substrate made according to a method comprising the steps of spreading the polymer solution onto a solid surface into a wet film and heating to a specified temperature, and is understood not to include polyaniline substrates that are formed and/or combined with a metal ion in solution.
  • Morphology dependent upon the acid dopant means that a particular add dopant reproducibly results in a specific morphology when applied under conditions specified herein with respect to acid dopant concentration, metal concentration, identity of the metal, time of immersion, etc.
  • the substrates of the present invention are dense-film substrates, which are comprised of a single, substantially uniform layer of a conductive polymer such as PANI.
  • a conductive polymer such as PANI.
  • production of the substrates of the present invention requires thermal treatment.
  • the substrates of the present invention are understood not to include substrates formed by mixing a metal ion and a polymer in solution, but rather, the metal is grown in situ after formation of the substrate.
  • metal-polyaniline composites are prepared by growing the metal particles on the substrate in situ, as opposed to depositing pre-formed metal structures onto a substrate.
  • the method of the present invention is suitable for inexpensively producing composites that in theory may be of any size ranging from a square millimeters to square meters.
  • the composites may be prepared by electrodeless deposition.
  • the reduction potential of PANI at its emeraldine base form versus a standard reference hydrogen electrode is from about 0.70 V to 0.75 V whereas PANI at its leucoemeraldine base form versus a standard reference hydrogen electrode is from about 0.30 V to 0.40 V.
  • the particular metal ions have a reduction potential greater than that of the PANI
  • immersion of a suitable PANI film or membrane into an aqueous solution of the particular metal ions can result in the deposition of metal upon the PANI and form the metal-PANI composite.
  • a metal coating including metal nanoparticies can form upon a PANI porous asymmetric membrane or thermally cured PANI dense film dipped into the aqueous metal salt solution.
  • Metals useful in the composite structures of the present invention can generally include metals such as gold, silver, platinum, palladium and the like.
  • Conducting polymers suitable for use in the present invention include conducting polymers such as polyaniline (PANI), polypyrrole, polythiophene, poly(phenylene vinylene), and combinations thereof.
  • the conducting polymer is polyaniline.
  • Polyaniline is the name given to the polymer having the structure, in a completely reduced leucoemeraldine oxidation state, of the general formula:
  • R is a hydrogen atom.
  • R may be a substituent such as an organic group, including, for example, CH 3 , C 2 H 5 , OCH 3 , N(CH 3 ) 2 , an inorganic group, including, for example, F, Cl, Br, I, or a metal chelate group.
  • an organic group including, for example, CH 3 , C 2 H 5 , OCH 3 , N(CH 3 ) 2
  • an inorganic group including, for example, F, Cl, Br, I, or a metal chelate group.
  • In situ deposition of metals on top of PANI surfaces can be achieved by immersing thermally cured dense PANI films into an aqueous metal ion solution with a wide range of metal ion concentrations.
  • the metal ion concentration ranges from about 0.001 Molar (M) to about 1.0 M.
  • the time period necessary for the metal growth ranges from about several seconds to about several hours depending upon the experimental conditions such as temperature and metal ion concentration.
  • the membranes are typically left in solution until metal deposition can he observed visually on the target surface.
  • the aqueous solution comprising the metal is first doped with a suitable acid, and a suitable substrate is then immersed in the aqueous solution.
  • the substrate is provided and doped with a suitable acid.
  • the doped membranes are then immersed into the aqueous solution comprising the metal.
  • the morphology and size of the nanostructures is dependent upon, and correlates to, the identity of the acid dopant.
  • Suitable acid dopants include, but are not limited to, hydrochloric acid (HCl), tartaric acid, camphosulfonic acid, phosphoric acid (H 3 PO 4 ), trifluoroacetic acid (CF 3 COOH), citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid), mandelic acid (2-phenyl-2-hydroxyacetic acid), poly(styrene sulfonic acid), para-tolueriesulfonic acid (p-CH 3 C 6 H 5 SO 3 H), and combinations thereof.
  • the resulting deposited metal nanostructures exhibited varying morphologies as seen in FIGS. 1-11 .
  • the morpohologies of the nanostructures include sheets, cubes, sheres (e.g., sphere-like dots, as shown in FIGS. 1 , 5 and 6 ), needles (e.g., needle-like structures, as shown in FIG. 2 ), rods (e.g., rod-like structures as shown in FIGS. 3 and 4 ), wires (e.g. as shown in FIG. 9 ), and random nanostructures (e.g., as shown in FIG. 11 ).
  • sheres e.g., sphere-like dots, as shown in FIGS. 1 , 5 and 6
  • needles e.g., needle-like structures, as shown in FIG. 2
  • rods e.g., rod-like structures as shown in FIGS. 3 and 4
  • wires e.g. as shown in FIG. 9
  • random nanostructures e.g., as shown in FIG. 11 ).
  • Metal deposition on the PANI membrane surfaces through reduction requires electron transfer from the PANI to the metal ions. As the metal ions approach the PANI membrane surface, they can be reduced by the PANI and form nuclei. In a conventional homogeneous system, where metal ions and a reducing agent are both dispersed in solution, the metal nuclei can serve as catalytic sites for subsequent surface growth allowing the formation of larger metal structures.
  • the present invention involves a heterogeneous system. In such a heterogeneous system, metal ions are reduced on the PANT membrane surface itself and the growth mechanism can be expected to differ from a homogeneous system.
  • the size of the metal nanoparticles is likely to be dominated, by the difference in reduction potential between metal ions and the PANI and by the surface properties, of the PANI membrane substrate.
  • the morphological difference corresponding to the various dopants may be influenced by the surface energy of the PANI membrane.
  • the surface energy of the PANI membrane manifested by the water contact angles, can be tuned by the nature of the dopants and the redox states of the PANI membrane.
  • Control of metal growth could also be achieved by using a stretched PANI film (a thermally cured PANI dense film).
  • the stretching of the PANI dense films can generally be from about 100 percent to 500 percent of the original size, more preferably from about 100 percent to about 400 percent of the original size.
  • the contrast between silver deposited on the stretched and unstretched PANI dense film is shown in FIG. 7 .
  • a preferential deposition of the silver on the PANI dense film surface coincided with the stretched direction.
  • the unstretched PANI dense films exhibited homogeneous silver deposition throughout the PANI dense film surface. Without wishing to be limited by theory, such a preferential silver deposition is thought to result from the lower reduction potential of the stretched oriented PANI dense film.
  • the stretched (extended) PNI chain conformation leads to formation of crystalline regions having lower reduction potential and higher conductivity that the unstretched film portions.
  • the metal-PANI composites of the present invention can provide good catalytic activity to various organic reactions especially toward hydrogenation reactions.
  • the metal e.g., metal nanoparticles
  • Pd on C typical commercially available metal catalysts
  • metal-PANI composites of the present invention wherein the metal is platinum or palladium can be used in the selective hydrogenation of alkenes and alkynes.
  • SERS Surface roughness has been considered an important factor that governs SERS. It has been previously observed that molecules near roughened silver surfaces show enhanced Raman scattering of as much as two orders of magnitude or more. The ability to detect and identify trace amounts of chemicals has become increasingly important. SERS has proven to be one of the most sensitive methods for performing chemical analysis by the detection of a single molecule. SERS offers the advantage of trace detection by increasing the scattering light intensity by as much as a factor of 10 10 , especially with nanostructured metals such as silver and gold.
  • the SERS effect leads to a major increase of the Raman scattering cross-section for molecules absorbed onto suitably rough metal surfaces.
  • use of the composites of the present invention in SERS applications has a large potential in analytical chemistry and for biological applications.
  • the structures of the present invention result in an enhancement of the localized electric field, which subsequently increases the SERS from the metal particles in the composite structures.
  • the formation of metals on reductive PANI surfaces can be controlled by tailoring the surface chemistry and redox potential.
  • a wide range of metal nanostructure morphologies can be achieved by selection of dopant.
  • the sizes of the deposited metal structures could also be varied from a few nanometers to several microns.
  • the composite materials of the present invention may further have application in surface processing, catalysis (e.g., in fuel cells or other chemical reactions), as modified surface electrodes, for anticorrosion and for biosensors.
  • N-Methyl-2-pyrrolidone (99% Aldrich), heptamethylenimine (HPMI, 98% Acros), citric acid (99.9% Fisher), silver nitrate (99.9999% Aldrich), hydrochloric acid (37%, Fisher), gold chloride (99%, Aldrich), 4-mercaptobenzoic acid (90%, Aldrich), and polyaniline emeraldine base (EB) powder (Aldrich) were used as received.
  • Spectroscopy All metallic substrates were prepared for spectroscopic analysis by forming a self assembled monolayer of 4-mercaptobenzoic acid (MBA) on their surface. Each substrate was immersed in a 5% ethanolic solution of MBA for 1 hour and then rinsed with fresh ethanol three times and allowed to air dry.
  • SERS Surface enhanced Raman spectra
  • SERS were recorded using approximately 1 mW, 785 nm. excitation focused onto the sample through a 0.5 NA microscope objective. The scattered Raman signal was collected in a backscattering configuration through the objective, filtered, and then dispersed onto a liquid nitrogen cooled CCD camera through a single grating spectrometer. All spectra were recorded using total integration times of 10 seconds.
  • PANI Starting Solution Concentrated PANI solutions (2.0% w/w) were prepared as follows. First, 1.15 g of EB powder was mixed with 0.747 g of heptamethyleneimine (HPMI) in a 12 mL Teflon vial for ten minutes with a spatula. Then, 4.14 g of N-methyl-2-pyrrolidinone (NMP) was added and stirred with a spatula for 30 minutes until the visible solid PANI particles were dispersed. The PANI solution was then filtered through a 10 mL syringe using a cotton plug.
  • HPMI heptamethyleneimine
  • NMP N-methyl-2-pyrrolidinone
  • PANI Thin Films The concentrated PANI solution was poured onto a glass substrate and smeared into a homogeneous thin film using a Gardner blade. The glass substrate and film were kept in a leveled oven at a 55° C. for two days to remove the solvents. The dried film was then detached from the glass substrate by immersing it in approximately 4 L water bath and then kept in the water bath overnight to ensure the removal of solvent residual (NMP and HPMI) by solvent exchange. The pristine PANI films were then dried in air for 1 hour, then sandwiched between two KimWipes, and placed under a flat metal weight (15 kg) for one day to keep the dry film flat.
  • NMP and HPMI solvent residual
  • the resulting thermally cured, dense PANI film has a thickness of 1 ⁇ m-350 ⁇ m (as measured by micrometer or vernier calipers) depending on the thickness setting of the Gardner blade.
  • the films were then doped by immersing them into an acid solution (typically in the concentration range from 0.01 M-0.25 M) for 24-144 hours followed by three rinses in 100 mL of purified water for 1-30 minutes.
  • Metal Nano Structures on PANI The acid doped films were cut into 5 ⁇ 5 mm pieces and immersed into freshly prepared aqueous metal ion solutions (AgNO 3 , or HAuCl 4 plus HCl) after which, metallic nanostructures immediately and spontaneously begin to form on the PANI surface. Rinsing the PAM film in water for 5 seconds halts all metal growth, and the metal structures are finally dried in air. Reaction conditions such as the PANI film thickness, the concentration of metal ion, and the total exposure time of the PANI film to the ion solution were all found to dramatically affect the resulting metal nanostructures.
  • aqueous metal ion solutions AlNO 3 , or HAuCl 4 plus HCl
  • FIGS. 1-4 contains representative SEM images of silver nanostructures formed on a 350 ⁇ m thick citric acid doped PANI film and SERS spectra of silver nanostructures grown at each respective concentration.
  • the silver structures were grown from silver nitrate solutions with concentrations of 1 mM ( FIG. 1 ), 10 mM ( FIG. 2 ), 20 mM ( FIGS. 3 ), and 100 mM ( FIG. 4 ).
  • the morphology varies with increasing silver ion concentration ranges from featureless particles to nanosheet assembly to rod-like assemblies. All of these silver nanoparticles exhibit strong SERS activity manifested by the SERS spectra of mercaptobenzoic acid (MBA).
  • MBA mercaptobenzoic acid
  • FIGS. 5-10 contain representative SEM images of silver nanostructures formed on a 150 ⁇ m PANI film which are doped with various acids having a pH of 1.5, and SERS spectra of silver nanostructures grown at 20 mM.
  • the PANI film were doped in tartaric acid ( FIG. 5 ), phosphoric acid ( FIG. 6 ), camphosulfonic acid ( FIG. 7 ), mandelic acid ( FIG. 8 ), p-toluene sulfonic acid ( FIG. 9 ), and poly(styrene sulfonic acid) ( FIG. 10 ).
  • the morphology of silver particles grown on PANI films is acid dependent. The morphology ranges from particles to wires. All of these silver nanoparticles exhibit SERS activity manifested by the SERS spectra of mercaptobenzoic acid (MBA).
  • MBA mercaptobenzoic acid
  • FIG. 11 shows representative SEM images of gold nanostructures formed on a 150 ⁇ m PANI film.
  • the gold structures were grown for overnight from a mixture, 2 mL of 200 mM AuCl 3 solution with 50 ⁇ L of 37% hydrochloric acid.
  • the gold structure has some sharp edges.
  • This Au particles exhibit SERS activity manifested by the SERS spectra of mercaptobenzoic acid (MBA).
  • MBA mercaptobenzoic acid
  • the Ag particles grown on PANI films with different thickness ranges from 50 to 340 ⁇ m also show variation in morphology and they also show SERS activity that appears to be somewhat morphological dependent. This result suggests another way of controlling the particle morphology as well as their corresponding SERS activity.
  • Ag particles were also grown on 150 ⁇ m thick undoped PANI films that were immersed in 1 ml of AgNO 3 solution (10 mM) containing a dopant (50 ⁇ l of citric acid—0.25 M).
  • This simultaneous doping and deposition process results in Ag metal nanostructures very similar to those observed with pre-dopped PANI films.
  • This co-doping/deposition method is general, and applies to any dopant of choice.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)

Abstract

Metal-polymer composites, and methods of making and use thereof, said composites comprising a thermally-cured dense polyaniline substrate; an acid dopant; and, metal nanostructure deposits wherein the deposits have a morphology dependent upon the acid dopant.

Description

CROSS REFERENCE TO RELATED APPLICATION
This application is a divisional of U.S. patent application Ser. No. 12/543,640 filed Aug. 19, 2009, which is a continuation-in-part of U.S. patent application Ser. No. 11/653,004, filed Jan. 11, 2007.
STATEMENT REGARDING FEDERAL RIGHTS
This invention was made with government support under Contract No. DE-AC52-06NA25396 awarded by the U.S. Department of Energy. The government has certain rights in the invention.
FIELD OF THE INVENTION
The present invention relates to metal-polyaniline composites, e.g., nanostructured metal-polyaniline composites, and to methods of preparation thereof.
BACKGROUND OF THE INVENTION
In the past few decades, there has been an increasing interest in using conducting polymers to fabricate electronic or optical devices such as light-emitting diodes and molecular electronics. Polyaniline (PANI) has been one of the most commonly used conducting polymers due to its facile synthesis, low cost and environmental stability, and has been carefully examined for use in electromagnetic shielding and anticorrosion coatings.
PANI possesses secondary and tertiary amines in the backbone structure that can reversibly bind metal ions. In cases where metal ions have a reduction potential higher than that of the PANI, the bound metal ions can be reduced to form zero-valent metals. Thus, it has been recognized that PANI can be used for the electrodeless deposition of metals from a metal ion solution.
When suitable acid dopants are used during the deposition of metals onto a surface, unique nanostructures may be formed which correlate to the type of acid dopant. Surprisingly, it was found that these metal, nanostructure-PANI composites were useful substrates for SERS (Surface Enhanced Raman Spectoscopy), and provided not only significantly increased sensitivity, but an inexpensive alternative to available substrates. Previous work employed an asymmetric, porous PANI substrate. It is desirable, however, to also be able to deposit metal nanostructures onto thermally-treated, dense PANI films, as such films are more easily obtained by thermally evaporating the solvent.
Previously, it was not thought that nanostructures could be successfully produced on dense film substrates. As described in U.S. patent application Ser. No. 11/653,004, the use of PANI porous asymmetric membranes for the chemical deposition of metal layers, e.g., nanostructured metal layers has an advantage of lower density. as compared to thermally cured dense PANI films. The lower density is thought to allow diffusion of metal ions between PANI chains, which may aid the nucleation process. Furthermore, the phase inversion process used to prepare the PANI membranes does not involve heat treatment for a prolonged time period. The phase inversion process allows PANI to maintain its original redox states and is believed to minimize crosslinking between PANI chains.
Previous attempts at growing metal nanostructures on non-porous substrates resulted in different metal morphologies as compared to those grown on porous asymmetric membranes. The growth of metals on the thermally cured dense films exhibited less variation in their morphologies. In general, silver growth on top of a series of thermally cured PANI dense films exhibited large microstructures with random morphologies. After further research, however, it has surprisingly been found that metal nanostructures having reproducible morphologies can be produced on non-porous substrates which are useful for a variety of applications, including SERS.
SUMMARY OF THE INVENTION
The present invention describes thermally treated, dense PANI films having a variety of nanostructures on the surface, and methods for controllably depositing the nanostructures.
The following describe some non-limiting embodiments of the present invention.
According to a first embodiment of the present invention, a method of forming a metal-polymer composite is provided, comprising providing a thermally-cured dense polyaniline substrate; contacting the thermally-cured dense polyaniline substrate with an acid dopant to form a doped substrate; providing a solution comprising a metal ion; and contacting the solution comprising a metal ion with the doped substrate, whereupon metal nanostructure deposits are formed on the doped substrate, wherein the deposits have a morphology which is dependent upon the acid dopant.
According to another embodiment of the present invention, a method of forming a metal-polymer composite is provided, comprising providing a thermally-cured dense polyaniline substrate; providing a solution comprising a metal ion and an acid dopant; and contacting the solution comprising the metal ion and acid dopant with the thermally-cured dense polyaniline substrate, whereupon metal nanostructure deposits are formed on the doped substrate, wherein the deposits have a morphology which is dependent upon the acid dopant.
According to yet another embodiment of the present invention, a method of performing surface-enhanced Raman spectral analysis of an analyte is provided, comprising providing a thermally-cured dense polyaniline substrate, wherein a surface of the substrate comprises metal nanostructure deposits and an acid dopant; bringing an analyte into effective contact with said metal-PANI composite; illuminating the metal-PANI composite with radiation of at least one wavelength for causing elemental-state particles to produce a plasmon field and for causing said plasmon field to interact with molecules of said analyte, in such a manner, so as to produce Raman photons; and, collecting scatted radiation emitted, from said metal-PANI composite for spectral analysis.
According to yet another embodiment of the present invention, a metal-polymer composite is provided, comprising a thermally-cured dense polyaniline substrate; an acid dopant; and, metal nanostructure deposits wherein the deposits have a morphology dependent upon the acid dopant.
BRIEF DESCRIPTION OF THE DRAWINGS
In all Figures, the x-axis represents wavelength in cm−1 and the y-axis represents signal intensity
FIGS. 1( a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 1 mM silver nitrate and doped with citric acid, and the corresponding SEM image of the nanostructure (b).
FIGS. 2( a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 10 mM silver nitrate, and the corresponding SEM image of the nanostructure (b). PANI dense film shown in (a); and, (d) the silver coated HCl doped PANI dense film shown in of the nanostructure (b).
FIGS. 3( a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with citric acid, and the corresponding SEM image of the nanostructure (b).
FIGS. 4( a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 100 mM silver nitrate and doped with citric acid, and the corresponding SEM image of the nanostructure (b).
FIGS. 5( a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with tartaric acid, and the corresponding SEM image of the nanostructure (b).
FIGS. 6( a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with phosphoric acid, and the corresponding SEM image of the nanostructure (b).
FIGS. 7( a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with camphosulfonic acid, and the corresponding SEM image of the nanostructure (b).
FIGS. 8 (a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with mandelic acid, and the corresponding SEM image of the nanostructure (b).
FIGS. 9 (a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with p-toluene sulfonic acid, and the corresponding SEM image of the nanostructure (b).
FIGS. 10 (a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a silver nanostructure of the present invention made with 20 mM silver nitrate and doped with polystyrene sulfonic acid, and the corresponding SEM image of the nanostructure (b).
FIGS. 11( a)-(b) show a SERS spectrum of mercaptobenzoic acid (MBA) (a) obtained from a gold nanostructure of the present invention made with 200 mM AuCl3 with HCl, and doped with citric acid, and the corresponding SEM image of the nanostructure (b).
DETAILED DESCRIPTION
The present invention is concerned with the metal-polyaniline composites comprising a dense-film PANI substrate, and to methods of producing these metal-polyaniline composites, wherein the metal forms various nanostructures on the surface of the composite. The present invention is also concerned with the use of such metal-polyaniline composites, e.g., such nanostructured metal-polyaniline composites, in applications employing Surface Enhanced Raman Scattering (SERS).
“Thermally-cured dense polyaniline substrate,” as used herein, means a substrate made according to a method comprising the steps of spreading the polymer solution onto a solid surface into a wet film and heating to a specified temperature, and is understood not to include polyaniline substrates that are formed and/or combined with a metal ion in solution.
“Morphology dependent upon the acid dopant,” as used herein, means that a particular add dopant reproducibly results in a specific morphology when applied under conditions specified herein with respect to acid dopant concentration, metal concentration, identity of the metal, time of immersion, etc.
The substrates of the present invention are dense-film substrates, which are comprised of a single, substantially uniform layer of a conductive polymer such as PANI. In contrast to asymmetric porous PANI membranes, which are produced by a solvent exchange process, production of the substrates of the present invention requires thermal treatment. The substrates of the present invention are understood not to include substrates formed by mixing a metal ion and a polymer in solution, but rather, the metal is grown in situ after formation of the substrate.
In the present invention, metal-polyaniline composites are prepared by growing the metal particles on the substrate in situ, as opposed to depositing pre-formed metal structures onto a substrate. In contrast to currently available SERS substrates, which are small in size and expensive to produce, the method of the present invention is suitable for inexpensively producing composites that in theory may be of any size ranging from a square millimeters to square meters. The composites may be prepared by electrodeless deposition. The reduction potential of PANI at its emeraldine base form versus a standard reference hydrogen electrode is from about 0.70 V to 0.75 V whereas PANI at its leucoemeraldine base form versus a standard reference hydrogen electrode is from about 0.30 V to 0.40 V. Where the particular metal ions have a reduction potential greater than that of the PANI, immersion of a suitable PANI film or membrane into an aqueous solution of the particular metal ions can result in the deposition of metal upon the PANI and form the metal-PANI composite. For silver nitrate (reduction potential of 0.8 V), gold chloride (reduction potential of 1.5 V), and platinum chloride (reduction potential of 0.755 V), a metal coating including metal nanoparticies can form upon a PANI porous asymmetric membrane or thermally cured PANI dense film dipped into the aqueous metal salt solution. Metals useful in the composite structures of the present invention can generally include metals such as gold, silver, platinum, palladium and the like.
Conducting polymers suitable for use in the present invention include conducting polymers such as polyaniline (PANI), polypyrrole, polythiophene, poly(phenylene vinylene), and combinations thereof. In one embodiment, the conducting polymer is polyaniline.
Polyaniline is the name given to the polymer having the structure, in a completely reduced leucoemeraldine oxidation state, of the general formula:
Figure US08148294-20120403-C00001
where n is greater than 5 and where R is a hydrogen atom. Alternatively, R may be a substituent such as an organic group, including, for example, CH3, C2H5, OCH3, N(CH3)2, an inorganic group, including, for example, F, Cl, Br, I, or a metal chelate group. For the polyanilines described herein, the appropriate choice of an R group permits a greater range of solubility in a greater number of different types of solvents, which results in increased versatility for processing the polymers and a greater range of chemical properties.
In situ deposition of metals on top of PANI surfaces can be achieved by immersing thermally cured dense PANI films into an aqueous metal ion solution with a wide range of metal ion concentrations. In one embodiment, the metal ion concentration ranges from about 0.001 Molar (M) to about 1.0 M. The time period necessary for the metal growth ranges from about several seconds to about several hours depending upon the experimental conditions such as temperature and metal ion concentration. The membranes are typically left in solution until metal deposition can he observed visually on the target surface.
In one embodiment of the present invention, the aqueous solution comprising the metal is first doped with a suitable acid, and a suitable substrate is then immersed in the aqueous solution. In an alternative embodiment, the substrate is provided and doped with a suitable acid. The doped membranes are then immersed into the aqueous solution comprising the metal. The morphology and size of the nanostructures is dependent upon, and correlates to, the identity of the acid dopant. Suitable acid dopants include, but are not limited to, hydrochloric acid (HCl), tartaric acid, camphosulfonic acid, phosphoric acid (H3PO4), trifluoroacetic acid (CF3COOH), citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid), mandelic acid (2-phenyl-2-hydroxyacetic acid), poly(styrene sulfonic acid), para-tolueriesulfonic acid (p-CH3C6H5SO3H), and combinations thereof. The resulting deposited metal nanostructures exhibited varying morphologies as seen in FIGS. 1-11.
The morpohologies of the nanostructures include sheets, cubes, sheres (e.g., sphere-like dots, as shown in FIGS. 1, 5 and 6), needles (e.g., needle-like structures, as shown in FIG. 2), rods (e.g., rod-like structures as shown in FIGS. 3 and 4), wires (e.g. as shown in FIG. 9), and random nanostructures (e.g., as shown in FIG. 11).
Metal deposition on the PANI membrane surfaces through reduction requires electron transfer from the PANI to the metal ions. As the metal ions approach the PANI membrane surface, they can be reduced by the PANI and form nuclei. In a conventional homogeneous system, where metal ions and a reducing agent are both dispersed in solution, the metal nuclei can serve as catalytic sites for subsequent surface growth allowing the formation of larger metal structures. The present invention involves a heterogeneous system. In such a heterogeneous system, metal ions are reduced on the PANT membrane surface itself and the growth mechanism can be expected to differ from a homogeneous system. While not wishing to he bound by the present explanation, the size of the metal nanoparticles is likely to be dominated, by the difference in reduction potential between metal ions and the PANI and by the surface properties, of the PANI membrane substrate. The morphological difference corresponding to the various dopants may be influenced by the surface energy of the PANI membrane. The surface energy of the PANI membrane, manifested by the water contact angles, can be tuned by the nature of the dopants and the redox states of the PANI membrane.
Control of metal growth could also be achieved by using a stretched PANI film (a thermally cured PANI dense film). The stretching of the PANI dense films can generally be from about 100 percent to 500 percent of the original size, more preferably from about 100 percent to about 400 percent of the original size. The contrast between silver deposited on the stretched and unstretched PANI dense film is shown in FIG. 7. A preferential deposition of the silver on the PANI dense film surface coincided with the stretched direction. In contrast, the unstretched PANI dense films exhibited homogeneous silver deposition throughout the PANI dense film surface. Without wishing to be limited by theory, such a preferential silver deposition is thought to result from the lower reduction potential of the stretched oriented PANI dense film. The stretched (extended) PNI chain conformation leads to formation of crystalline regions having lower reduction potential and higher conductivity that the unstretched film portions.
The metal-PANI composites of the present invention can provide good catalytic activity to various organic reactions especially toward hydrogenation reactions. As the metal., e.g., metal nanoparticles, are stably adfixed to the PANI membrane, it can be easily recycled and reused whereas typical commercially available metal catalysts, e.g., Pd on C, can only be used once.
In one embodiment, metal-PANI composites of the present invention wherein the metal is platinum or palladium can be used in the selective hydrogenation of alkenes and alkynes.
Surface roughness has been considered an important factor that governs SERS. It has been previously observed that molecules near roughened silver surfaces show enhanced Raman scattering of as much as two orders of magnitude or more. The ability to detect and identify trace amounts of chemicals has become increasingly important. SERS has proven to be one of the most sensitive methods for performing chemical analysis by the detection of a single molecule. SERS offers the advantage of trace detection by increasing the scattering light intensity by as much as a factor of 1010, especially with nanostructured metals such as silver and gold.
The SERS effect leads to a major increase of the Raman scattering cross-section for molecules absorbed onto suitably rough metal surfaces. Thus, use of the composites of the present invention in SERS applications has a large potential in analytical chemistry and for biological applications. The structures of the present invention result in an enhancement of the localized electric field, which subsequently increases the SERS from the metal particles in the composite structures.
Through the process of the present invention, the formation of metals on reductive PANI surfaces can be controlled by tailoring the surface chemistry and redox potential. A wide range of metal nanostructure morphologies can be achieved by selection of dopant. The sizes of the deposited metal structures could also be varied from a few nanometers to several microns. The composite materials of the present invention may further have application in surface processing, catalysis (e.g., in fuel cells or other chemical reactions), as modified surface electrodes, for anticorrosion and for biosensors.
The present invention is more particularly described in the following examples which are intended as illustrative only.
EXAMPLES
Reagents: N-Methyl-2-pyrrolidone (99% Aldrich), heptamethylenimine (HPMI, 98% Acros), citric acid (99.9% Fisher), silver nitrate (99.9999% Aldrich), hydrochloric acid (37%, Fisher), gold chloride (99%, Aldrich), 4-mercaptobenzoic acid (90%, Aldrich), and polyaniline emeraldine base (EB) powder (Aldrich) were used as received.
Microscopy: PANI membrane surfaces were imaged using either a JEOL 6300FXV SEM or a FEI Quanta FEG ESEM.
Spectroscopy: All metallic substrates were prepared for spectroscopic analysis by forming a self assembled monolayer of 4-mercaptobenzoic acid (MBA) on their surface. Each substrate was immersed in a 5% ethanolic solution of MBA for 1 hour and then rinsed with fresh ethanol three times and allowed to air dry. Surface enhanced Raman spectra (SERS) were recorded using approximately 1 mW, 785 nm. excitation focused onto the sample through a 0.5 NA microscope objective. The scattered Raman signal was collected in a backscattering configuration through the objective, filtered, and then dispersed onto a liquid nitrogen cooled CCD camera through a single grating spectrometer. All spectra were recorded using total integration times of 10 seconds.
PANI Starting Solution: Concentrated PANI solutions (2.0% w/w) were prepared as follows. First, 1.15 g of EB powder was mixed with 0.747 g of heptamethyleneimine (HPMI) in a 12 mL Teflon vial for ten minutes with a spatula. Then, 4.14 g of N-methyl-2-pyrrolidinone (NMP) was added and stirred with a spatula for 30 minutes until the visible solid PANI particles were dispersed. The PANI solution was then filtered through a 10 mL syringe using a cotton plug.
PANI Thin Films: The concentrated PANI solution was poured onto a glass substrate and smeared into a homogeneous thin film using a Gardner blade. The glass substrate and film were kept in a leveled oven at a 55° C. for two days to remove the solvents. The dried film was then detached from the glass substrate by immersing it in approximately 4 L water bath and then kept in the water bath overnight to ensure the removal of solvent residual (NMP and HPMI) by solvent exchange. The pristine PANI films were then dried in air for 1 hour, then sandwiched between two KimWipes, and placed under a flat metal weight (15 kg) for one day to keep the dry film flat. The resulting thermally cured, dense PANI film has a thickness of 1 μm-350 μm (as measured by micrometer or vernier calipers) depending on the thickness setting of the Gardner blade. The films were then doped by immersing them into an acid solution (typically in the concentration range from 0.01 M-0.25 M) for 24-144 hours followed by three rinses in 100 mL of purified water for 1-30 minutes.
Metal Nano Structures on PANI: The acid doped films were cut into 5×5 mm pieces and immersed into freshly prepared aqueous metal ion solutions (AgNO3, or HAuCl4 plus HCl) after which, metallic nanostructures immediately and spontaneously begin to form on the PANI surface. Rinsing the PAM film in water for 5 seconds halts all metal growth, and the metal structures are finally dried in air. Reaction conditions such as the PANI film thickness, the concentration of metal ion, and the total exposure time of the PANI film to the ion solution were all found to dramatically affect the resulting metal nanostructures.
Example 1
FIGS. 1-4 contains representative SEM images of silver nanostructures formed on a 350 μm thick citric acid doped PANI film and SERS spectra of silver nanostructures grown at each respective concentration. The silver structures were grown from silver nitrate solutions with concentrations of 1 mM (FIG. 1), 10 mM (FIG. 2), 20 mM (FIGS. 3), and 100 mM (FIG. 4). The morphology varies with increasing silver ion concentration ranges from featureless particles to nanosheet assembly to rod-like assemblies. All of these silver nanoparticles exhibit strong SERS activity manifested by the SERS spectra of mercaptobenzoic acid (MBA). The SERS signal is collected under 1 mW of laser power and a collection time of 10 secs.
Example 2
FIGS. 5-10 contain representative SEM images of silver nanostructures formed on a 150 μm PANI film which are doped with various acids having a pH of 1.5, and SERS spectra of silver nanostructures grown at 20 mM. The PANI film were doped in tartaric acid (FIG. 5), phosphoric acid (FIG. 6), camphosulfonic acid (FIG. 7), mandelic acid (FIG. 8), p-toluene sulfonic acid (FIG. 9), and poly(styrene sulfonic acid) (FIG. 10). The morphology of silver particles grown on PANI films is acid dependent. The morphology ranges from particles to wires. All of these silver nanoparticles exhibit SERS activity manifested by the SERS spectra of mercaptobenzoic acid (MBA). The SERS signal is collected under 1 mW of laser power and a collection time of 10 secs.
Example 3
FIG. 11 shows representative SEM images of gold nanostructures formed on a 150 μm PANI film. The gold structures were grown for overnight from a mixture, 2 mL of 200 mM AuCl3 solution with 50 μL of 37% hydrochloric acid. The gold structure has some sharp edges. This Au particles exhibit SERS activity manifested by the SERS spectra of mercaptobenzoic acid (MBA). The SERS signal is collected under 1 mW of laser power and a collection time of 10 secs.
Example 4
The Ag particles grown on PANI films with different thickness ranges from 50 to 340 μm also show variation in morphology and they also show SERS activity that appears to be somewhat morphological dependent. This result suggests another way of controlling the particle morphology as well as their corresponding SERS activity.
Example 5
Ag particles were also grown on 150 μm thick undoped PANI films that were immersed in 1 ml of AgNO3 solution (10 mM) containing a dopant (50 μl of citric acid—0.25 M). This simultaneous doping and deposition process results in Ag metal nanostructures very similar to those observed with pre-dopped PANI films. This co-doping/deposition method is general, and applies to any dopant of choice.

Claims (14)

What is claimed is:
1. A method of forming a metal-polymer composite comprising:
a) providing a thermally-cured dense polyaniline substrate;
b) contacting the thermally-cured dense polyaniline substrate with an acid dopant to form a doped substrate;
c) providing a solution comprising a metal ion; and
d) contacting the solution comprising a metal ion with the doped substrate, whereupon metal nanostructure deposits are formed on the doped substrate, wherein the deposits have a morphology which is dependent upon the acid dopant.
2. The method of claim 1, wherein the metal is selected from the group consisting of silver and gold.
3. The method of claim 1, wherein the acid dopant is selected from the group consisting of tartaric acid, camphosulfonic acid, phosphoric acid, citric acid, mandelic acid, poly(styrene sulfonic acid), para-toluenesulfonic acid, and combinations thereof.
4. The method of claim 1, wherein the nanostructure deposits are sheets, cubes, spheres, needles, rods, or wires.
5. The method of claim 4, wherein the nanostructure deposits are wires.
6. The method of claim 1, wherein the metal is silver and the acid dopant is citric acid.
7. The method of claim 1, wherein the metal is silver, the acid dopant is para-toluenesulfonic acid, and the nanostructure deposits are wires.
8. A method of forming a metal-polymer composite comprising:
a) providing a thermally-cured dense polyaniline substrate;
b) providing a solution comprising a metal ion and an acid dopant; and
c) contacting the solution comprising the metal ion and acid dopant with the thermally-cured dense polyaniline substrate, whereupon metal nanostructure deposits are formed on the doped substrate, wherein the deposits have a morphology which is dependent upon the acid dopant.
9. The method of claim 8, wherein the acid dopant is selected from the group consisting of tartaric acid, camphosulfonic acid, phosphoric acid, citric acid, mandelic acid, poly(styrene sulfonic acid), para-toluenesulfonic acid, and combinations thereof.
10. The method of claim 8, wherein the nanostructure deposits are sheets, cubes, spheres, needles, rods, or wires.
11. A method of performing surface-enhanced Raman spectral analysis of an analyte comprising:
a) providing a a thermally-cured dense polyaniline substrate, wherein a surface of the substrate comprises metal nanostructure deposits and an acid dopant;
b) bringing an analyte into effective contact with said metal-PANI composite;
c) illuminating the metal-PANI composite with radiation of at least one wavelength for causing elemental-state particles to produce a plasmon field and for causing said plasmon field to interact with molecules of said analyte, in such a manner, so as to produce Raman photons; and,
d) collecting scatted radiation emitted from said metal-PANI composite for spectral analysis.
12. The method of claim 11, wherein the metal is selected from the group consisting of silver and gold.
13. The method of claim 11, wherein the acid dopant is selected from the group consisting of tartaric acid, camphosulfonic acid, phosphoric acid, citric acid, mandelic acid, poly(styrene sulfonic acid), para-toluenesulfonic acid, and combinations thereof.
14. The method of claim 11, wherein the nanostructure deposits are sheets, cubes, spheres, needles, rods, or wires.
US13/196,735 2007-01-11 2011-08-02 Metal-polymer composites comprising nanostructures and applications thereof Expired - Fee Related US8148294B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US13/196,735 US8148294B2 (en) 2007-01-11 2011-08-02 Metal-polymer composites comprising nanostructures and applications thereof

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US11/653,004 US7786037B2 (en) 2007-01-11 2007-01-11 Nanostructured metal-polyaniline composites
US12/543,640 US7988887B2 (en) 2007-01-11 2009-08-19 Metal-polymer composites comprising nanostructures and applications thereof
US13/196,735 US8148294B2 (en) 2007-01-11 2011-08-02 Metal-polymer composites comprising nanostructures and applications thereof

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US12/543,640 Division US7988887B2 (en) 2007-01-11 2009-08-19 Metal-polymer composites comprising nanostructures and applications thereof

Publications (2)

Publication Number Publication Date
US20110293820A1 US20110293820A1 (en) 2011-12-01
US8148294B2 true US8148294B2 (en) 2012-04-03

Family

ID=42098568

Family Applications (2)

Application Number Title Priority Date Filing Date
US12/543,640 Expired - Fee Related US7988887B2 (en) 2007-01-11 2009-08-19 Metal-polymer composites comprising nanostructures and applications thereof
US13/196,735 Expired - Fee Related US8148294B2 (en) 2007-01-11 2011-08-02 Metal-polymer composites comprising nanostructures and applications thereof

Family Applications Before (1)

Application Number Title Priority Date Filing Date
US12/543,640 Expired - Fee Related US7988887B2 (en) 2007-01-11 2009-08-19 Metal-polymer composites comprising nanostructures and applications thereof

Country Status (1)

Country Link
US (2) US7988887B2 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130070241A1 (en) * 2011-09-15 2013-03-21 Zhiyong Li Asymmetrical-nanofinger device for surface-enhanced luminescense
US9001324B2 (en) 2010-07-30 2015-04-07 Hewlett-Packard Development Company, L.P. Optical fiber surface enhanced raman spectroscopy (SERS) probe
US9244015B2 (en) 2010-04-20 2016-01-26 Hewlett-Packard Development Company, L.P. Self-arranging, luminescence-enhancement device for surface-enhanced luminescence
US9274058B2 (en) 2010-10-20 2016-03-01 Hewlett-Packard Development Company, L.P. Metallic-nanofinger device for chemical sensing
US9279767B2 (en) 2010-10-20 2016-03-08 Hewlett-Packard Development Company, L.P. Chemical-analysis device integrated with metallic-nanofinger device for chemical sensing

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2887556C (en) * 2012-10-12 2021-01-12 The Regents Of The University Of California Polyaniline membranes with increased hydrophilicity
ES2893539T3 (en) 2013-05-15 2022-02-09 Univ California Polyaniline membranes formed by phase inversion for forward osmosis applications
WO2015157227A1 (en) 2014-04-08 2015-10-15 The Regents Of The University Of California Polyaniline-based chlorine resistant hydrophilic filtration membranes
JP2017018910A (en) * 2015-07-13 2017-01-26 ＣＯ２Ｍ‐Ｔｅｃｈ株式会社 Composite membrane and production method for the same
CN105461920B (en) * 2015-12-16 2018-02-23 华南师范大学 Method and the application of one pot process sea urchin shape golden nanometer particle and spherical polyaniline

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9244015B2 (en) 2010-04-20 2016-01-26 Hewlett-Packard Development Company, L.P. Self-arranging, luminescence-enhancement device for surface-enhanced luminescence
US9001324B2 (en) 2010-07-30 2015-04-07 Hewlett-Packard Development Company, L.P. Optical fiber surface enhanced raman spectroscopy (SERS) probe
US9274058B2 (en) 2010-10-20 2016-03-01 Hewlett-Packard Development Company, L.P. Metallic-nanofinger device for chemical sensing
US9279767B2 (en) 2010-10-20 2016-03-08 Hewlett-Packard Development Company, L.P. Chemical-analysis device integrated with metallic-nanofinger device for chemical sensing
US9594022B2 (en) 2010-10-20 2017-03-14 Hewlett-Packard Development Company, L.P. Chemical-analysis device integrated with metallic-nanofinger device for chemical sensing
US20130070241A1 (en) * 2011-09-15 2013-03-21 Zhiyong Li Asymmetrical-nanofinger device for surface-enhanced luminescense
US8520202B2 (en) * 2011-09-15 2013-08-27 Hewlett-Packard Development Company, L.P. Asymmetrical-nanofinger device for surface-enhanced luminescense

Also Published As

Publication number Publication date
US20100091275A1 (en) 2010-04-15
US20110293820A1 (en) 2011-12-01
US7988887B2 (en) 2011-08-02

Similar Documents

Publication Publication Date Title
US8148294B2 (en) Metal-polymer composites comprising nanostructures and applications thereof
US8279435B2 (en) Nanostructured metal-polyaniline composites and applications thereof
Liu et al. Plasmonic coupling of Au nanoclusters on a flexible MXene/Graphene oxide fiber for ultrasensitive SERS sensing
Choi et al. Electrospun nanostructures for high performance chemiresistive and optical sensors
Huang et al. Green in situ synthesis of clean 3D chestnutlike Ag/WO3–x nanostructures for highly efficient, recyclable and sensitive SERS sensing
Han et al. Effect of oxidation on surface-enhanced Raman scattering activity of silver nanoparticles: a quantitative correlation
Mondal et al. Facile decoration of polyaniline fiber with Ag nanoparticles for recyclable SERS substrate
Zhang et al. Biomimetic synthesis of hierarchical 3D Ag butterfly wing scale arrays/graphene composites as ultrasensitive SERS substrates for efficient trace chemical detection
Liu et al. Preparation of Au/PAN nanofibrous membranes for catalytic reduction of 4-nitrophenol
Bian et al. Reproducible and recyclable SERS substrates: Flower-like Ag structures with concave surfaces formed by electrodeposition
Vendamani et al. Silicon nanostructures for molecular sensing: a review
WO2001039873A1 (en) Hydroxylamine seeding of colloidal metal nanoparticles
Zhou et al. A silver-grafted sponge as an effective surface-enhanced Raman scattering substrate
Wang et al. Self-assembled silver nanoparticle films at an air–liquid interface and their applications in SERS and electrochemistry
Huang et al. Island-like nanoporous gold: smaller island generates stronger surface-enhanced Raman scattering
Krutyakov et al. Synthesis of highly stable silver colloids stabilized with water soluble sulfonated polyaniline
CN104251852A (en) Surface enhanced Raman scattering substrate constructed by electroless deposition and preparation method and application thereof
Lu et al. Facile method to fabricate cactus-like Ag NPs/CuO/Cu2O nanocomposites for recyclable SERS detection of trace carbendazim residues
Bauer et al. Synthesis of 3D dendritic gold nanostructures assisted by a templated growth process: application to the detection of traces of molecules
Trang et al. Hotspot-type silver-polymers grafted nanocellulose paper with analyte enrichment as flexible plasmonic sensors for highly sensitive SERS sensing
Huang et al. Self-assembled dendrite Ag arrays with tunable morphologies for surface-enhanced Raman scattering
Mohanty et al. Au/SnS2 Hybrid Quantum Dots for Surface-Enhanced Raman Scattering-Based Monitoring and Photoreduction of Hg (II) Ions
Broens et al. Highly ordered TiO2 nanotube films photo-decorated with Ag nanoparticles as SERS platforms: Relationship between morphology and enhancement
Xia et al. Facile fabrication of hierarchically flowerlike Ag microstructure for SERS application
Jia et al. Controlled growth of polyhedral and plate-like Ag nanocrystals on a nanofiber mat as a SERS substrate

Legal Events

Date Code Title Description
STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

AS Assignment

Owner name: TRIAD NATIONAL SECURITY, LLC, NEW MEXICO

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LOS ALAMOS NATIONAL SECURITY, LLC;REEL/FRAME:048007/0874

Effective date: 20181031

FEPP Fee payment procedure

Free format text: MAINTENANCE FEE REMINDER MAILED (ORIGINAL EVENT CODE: REM.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

LAPS Lapse for failure to pay maintenance fees

Free format text: PATENT EXPIRED FOR FAILURE TO PAY MAINTENANCE FEES (ORIGINAL EVENT CODE: EXP.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362

FP Lapsed due to failure to pay maintenance fee

Effective date: 20200403